Modern Principles of Shaping - 4. Relax criteria when something changes!

I'm writing a 10 part blog post where I discuss the Modern Principles of Shaping by Karen Pryor, to help solidify them in my mind.

4. Relax criteria when something changes. When introducing a new criterion or aspect of the skill, temporarily relax the old criteria for previously mastered skills.

 

1. Introducing a criteria could be, for a human, spelling out what you want that person to do.  In this case, use only 5 words, use a positive statement, and make it memorable/measurable. 
2.  For non-verbal (differently abled, animals), begin rewarding a different criteria, but be lenient on the other.  This can be a hard experience, because the subject is now being rewarded for something different than before.  
3. When you relax the old criteria, use your judgement about how much to relax it.  For the first few C/T, relax it completely, to the point that you're not looking for it at all.  
4. When the new criteria is trained up, you can begin adding the first criteria back in.  The learner needs to be able to do both of the criteria before you ask for both.  
5. Don't lose heart that the learner seems to have lost all the things he learned.  You relax the criteria because the learner WILL be more variable in what they know until they know the new criteria. 

Outstanding Questions: How many times should you repeat something?  Should the same criteria be used for multiple rewards in a single session?  Or is switching between criteria every C/T OK?